1. Field of the Invention
This invention relates in general to systems in which substances are transferred from one location to another and to the fitting which connects those two locations and through which a substance flows. More specifically, this invention relates to LP gas cylinder valves.
2. Description of the Prior Art
Systems which transfer fluid or gaseous substances from one point to another, normally employ some type of fitting for connecting the outlet aperture of a storage container to the inlet of the point of usage. Such fittings may be designed as valves for metering control or as male-female adaptors for straight connecting applications.
Typical of such a connection fitting is one which includes an externally-threaded hollow cylinder and a hollow stem with an enlarged, bullet-shaped head, slidably extending through said cylinder. The cylinder will be threadedly received by the outlet aperture of the container and when tightened into position, the bullet-shaped head of the stem is forced into sealing engagement with the outlet aperture. If the sealing engagement is complete, substances will only flow through the hollow stem and not around the bullet-shaped head. An LP gas valve and LP gas tank are typical examples of the connecting structure just described, and Blocker, U.S. Pat. No. 3,947,942 discloses the structure of such a valve in detail.
Due in part to sealing imperfections with either soft or hard nose designs, as well as to internal pressures, the substance, especially when gaseous in nature, may leak to the atmosphere rather than be transferred through the connection. The passageway for such a leak may be between the hollow cylinder and the hollow stem or it may be between the threaded connection of the cylinder and the outlet aperture. Depending upon the type of substance being transferred and the particular application, it may be necessary to determine if the fitting is leaking. Under the situation just described, detection of such a leak would require application of a leak-test solution at two different locations. There are several designs for couplings and fittings which include leak-directing passageways for channeling the leaks to a single location. Brown, U.S. Pat. No. 1,497,652 and Weber, U.S. Pat. No. 3,489,435 disclose two such designs. There are disadvantages with such devices in that the location of where to test for leaks is not readily apparent nor is there a convenient procedure for applying the leak-test solution and retaining the solution at the test location. If there is a slow leak, this solution may run off or evaporate before detection can be made.